Background and Objectives: Due to the high nutritional value of milk, it has an important role in human nutrition, and on the other hand, it is a suitable medium for the growth of bacteria, such as Pseudomonas aeruginosa. Pseudomonas aeruginosa, is an opportunistic pathogen highly resistant to antibiotics and can cause disease in immunodeficient patients. The purpose of this study was isolation of Pseudomonasaeruginosa from raw milk, detection of tox A gene by PCR, and determining antibiotic resistance, multiple resistance of the isolates, and Identification of ESBL isolates.

Methods: In this cross-sectional study, a total of 360 samples (300 samples of raw milk, 30 samples pasteurized milk, and 30 samples of cream), were collected from animal husbandries and stores in Qom city. Initially, the isolates of Pseudomonas aeruginosa, were confirmed by standard microbiological methods, and then the existence of exotoxin A gene in all isolates was detected by PCR method and the antibiotic resistance of the isolates against 10 antibiotics selected from different antibiotic categories, was investigated according to the CLSI standard. The data were analyzed using t-test.

Results: Out of 360 studied samples, 117 Pseudomonas aeruginosa were isolated, among which 101 strains (86.30%) had tox A gene. In antibiotic resistance testing, the highest resistance was seen against ceftazidime, and it was revealed that there is a significant relationship between the presence of tox A gene and antibiotic resistance in the isolates of Pseudomonas aeruginosa.

Conclusion: Due to high presence of Pseudomonas aeruginosa in raw milk and existence of antibiotic resistance genes in this bacterium, applying appropriate strategies for hygiene control in animal husbandries, is necessary to prevent the spread of bacteria.